1. Field of the Invention
The present invention relates to a process for refining a crude wine. More particularly, it relates to a process for preparing a refined wine in which tartar precipitate is not formed during storage.
2. Description of the Prior Art
In recent years, the consumption of and demand for wine have greatly increased.
However, conventional and traditional methods are still employed in the preparation of wine, i.e., modernization and the introduction of new concepts has been relatively slow. The major reason for this trend is that even a minor modification of the process can cause significant deterioration of color, tone, taste, aroma and cloudiness due to tartar formation, all of which are very important for the quality of wine. On the other hand, the increased demand for wine makes new processes capable of producing good, cheap wines very attractive.
Therefore, if a wine could be supplied cheaply in large quantities without a concomitant deterioration in its quality by improving and conceptualizing in a modern way the techniques of wine making, a very desirable advance in the art would be obtained.
In the preparation of wine, the fermentation process is undoubtedly the decisive factor in the resultant quality of the wine. However, the prevention of the formation of dregs such as tartar during fermentation or during curing after the completion of fermentation is also an extremely important factor in the production of wine as a saleable commodity.
The conventional process for refining wine may be summarized as follows:
When fermentation is completed the wine (hereinafter referred to as "crude wine") is racked off, or separated from the lees or sediment. Racking may be repeated several times at intervals, the crude wine being stored in wooden cooperages where aging takes place. The crude wine is then cleared before bottling. Fining agents such as isinglass, gelatin or bentonite clay are used, assisted by processes such as heat treatment, refrigeration and filtration. When a refined wine is bottled young, a special chilling to remove excess tartar is necessary. Even so, the wine frequently produces a slight deposit when aged in the bottle for several years. The refined wine, which has been processed through dreg-separation and subsequent aging, is bottled and marketed as a commodity. Thus, the conventional process for refining wine has an enormous disadvantage in that it is laborious and time-consuming since repeated dreg separation is required. Furthermore, in the conventional method for refining wine, it is very difficult to control the amount of tartar that is precipitated during the aging process so that tartar often precipitates from the wine after bottling.
Recently, a process for refining wine comprising promoting the precipitation of tartar by chilling a crude wine to -4.degree. C to 5.degree. C using a cooling device (Journal of the Japan Brewing Association, 63, 951 (1968) and a process for refining wine by repeated alternative cooling and heating have been developed. However, these refining processes have similar disadvantages to the conventional processes, because dreg separation must be frequently conducted. In principle, it is necessary to completely remove tartar from a crude wine before bottling. Thus, the removal and precipitation of tartar should be controllable at will and easily performable in wine manufacturing. Nevertheless, the procedures which conventionally have been employed or those which are suggested in publications are invariably dependent upon the process of separating tartar by storing crude wine in a barrel for a long period or by cooling crude wine. Essentially, the need for an effective process for tartar removal from wine remains unfulfilled.
The treatment of wine by electrodialysis using an ion-exchange membrane in order to remove acids and ions therefrom has been reported (Bulletin of the Research Institute of Fermentation, Yamanashi University, Japan, No. 6, pp. 1 to 6, 1959). The process described in this article involves placing wine into the center chamber of an ion-exchange membrane electrodialysis apparatus having electrode chambers containing 0.02% salt solutions on both sides and applying direct current between both electrodes to effect ion migration from the wine into the 0.02% solution of salt. (See FIG. 6 on page 2 of the above-cited reference.) According to this report, the flavor of the wine was not adversely affected after the electrodialysis while pH elevation, lowering of the titration acidity and decrease of calcium, magnesium, iron and copper content were observed. This process, however, is burdened with several significant defects:
1. The flavoring components are simultaneously removed during tartar removal and the flavor of the wine worsens;
2. In view of the mechanism of the electrodialysis apparatus and the principle of electrodialysis, mixing of water or the salt solution into the wine is inevitable; and
3. the pH of the wine rises remarkably and the color tone of the wine is changed.
Therefore, simple application of an ion-exchange membrane electrodialysis to a crude wine for partial removal of tartar-forming components results in appreciable deterioration in the flavor and in other inherent indispensible qualities of the wine.
From the foregoing discussion, it is obvious that it would be most desirable to have a process for simple removal of tartar in wine without affecting the flavor and other inherent properties of the refined wine.